1. Field of the Invention
The present invention relates to a nanocomposite composition having superior barrier properties and an article comprising the same, and more particularly to a nanocomposite composition having superior mechanical strength and superior oxygen, organic solvent, and moisture barrier properties, which can be used in single/multi-layer blow molding and film processing, and an article using the same.
2. Description of the Related Art
General-purpose resins, such as polyethylene and polypropylene, are used in many fields due to their superior moldability, mechanical properties, and moisture barrier properties. While these resins have good gas barrier properties as well, they are limited in their use in packaging or containers for agrochemicals and foods, which require superior chemical and oxygen barrier properties. Therefore, packaging or containers (e.g., bottles) for such materials are manufactured with multi-layers by co-extrusion, lamination, coating, etc.
Multi-layer plastic products composed of an ethylene-vinyl alcohol (EVOH) copolymer and polyamide are transparent and have good gas barrier properties. However, because ethylene-vinyl alcohol copolymer and polyamide resins are more expensive than general-purpose resins, the amount of these resins used is limited, and the ethylene-vinyl alcohol and polyamide resins should be formed as thin as possible.
To reduce the production costs of multi-layer plastic containers, a method of compounding ethylene-vinyl alcohol and polyamide resins with a more inexpensive polyolefin has been proposed. However, because ethylene-vinyl alcohol and polyamide are not very compatible with polyolefin, the blending is not easy. If ethylene-vinyl alcohol and polyamide are blended insufficiently, the mechanical properties of produced films or sheets become poor.
Thus, a method of using a compatibilizer to increase the compatibility of ethylene-vinyl alcohol and polyamide resin with polyolefin has been proposed. Because the compatibilizer increases compatibility of ethylene-vinyl alcohol and polyamide resin with polyolefin, which is necessary to provide a product with good mechanical strength and chemical barrier properties.
U.S. Pat. No. 4,971,864, U.S. Pat. No. 5,356,990, EP No. 15,556, and EP No. 210,725 disclose methods of using a compatibilizer prepared by grafting polyethylene with maleic anhydride. While this compatibilizer improves oxygen barrier properties and mechanical strength, moisture barrier properties are poor due to the hydrophilic properties of ethylene-vinyl alcohol, polyamide resin and ionomers. Therefore, hydrophobic resin processing at the outermost layer is necessary, and there is no suitable processing condition for obtaining an effective barrier property morphology.
As disclosed in U.S. Pat. Nos. 4,739,007, 4,618,528, 4,874,728, 4,889,885, 4,810,734, and 5,385,776, a nanocomposite contains exfoliated or intercalated platelets, tactoidal structures, or a dispersion mixture thereof, the particles having nanometer dimensions, and intercalated clay dispersed in a matrix polymer, such as an oligomer, a polymer, or a blend thereof.
In general, the manufacturing of nanocomposites is divided into two methods.
The first method is the manufacturing method of the above-described polyamide nanocomposite. In this method, monomers are inserted into intercalated organic clay, and the clay platelets are dispersed through inter-layer polymerization. This method is restricted in that it is applicable only when cationic polymerization is possible.
The other method is a melt compounding method in which melted polymer chains are inserted into intercalated clay and exfoliated through mechanical compounding. Examples of such a method are disclosed in “Preparation of polystyrene nanocomposite” (R. A. Vaia, et. al, Chem. Mater., 5, 1694(1993)), “Preparation of polypropylene nanocomposite” (M. Kawasumi, et. al, Macromolecules, 30, 6333(1997)), and “Preparation of nylon 6 nanocomposite” (U.S. Pat. No. 5,385,776), etc.
Therefore, a nanocomposite having superior mechanical strength and chemical barrier properties that is capable of realizing effective barrier property morphology is needed.